DE2032928A1 - Process for pre-treating metal objects - Google Patents

Description

Continental Can Company, Inc., üfew York 17 «NY / USA,

633 Third Avenue

"Process for the pretreatment of metal objects" -_— - - - -. - - - - - - ■ "". "■" ■ - ■ ---------- _ f

The invention relates to a method for pretreating metal objects to the surface of which an object made of a propylene polymer is to be glued. The invention further relates to an article, in particular a Aufreißbehälterteil with a container mirror which is provided with a lacquer coating, and having a preformed opening, which comparable with a detachable cover a is concluded.

The present invention is concerned with the object To attach objects made of a propylene polymer to metal surfaces. This task concerns the area metallic containers that use propylene polymer lids.

AufrtiJifctnältr »has long been known - such Containers are generally made of metal - and |

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provided with a pouring or removal opening. This pouring opening usually only takes up part of the area of a lid surface of the container. So far the pouring opening has been by a weakening or bit line in the material defined, which represented a tear strip. A pull handle was attached to the tear strip. After applying a corresponding tensile force, the tear strip along the weakening line from the surrounding area of the Cut out the mirror.

Although these easy-open containers have been quickly accepted by consumers, there is still a certain kind of reluctance to use them. This is due, for example, the fact that the detachable Aufreißstreif has s after the tearing out of the can lid sharp edges. If the tear-off part or strip is simply thrown on the floor or improperly picked up, then there is a risk of cuts.

Eb has already been suggested to replace the metallic tear strip with a plastic cover because then the risk of fray injuries is avoided. ¹ f _e il "does not have any sharp edges that can lead to solvent loss, such plastic deo &

Resin, for example

jedocli at the same time tightly alieotolieleiad ai Ä ^ isaisfaig ^: ä. ©! ¹ "Off

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pouring opening in the lid surface attached by forming an adhesive connection by means of a suitable adhesive. In the case of cover mirrors intended for beverage containers or the like, a coating of an adhesive was applied to the surface, which could be activated by heating in order to effect the connection of the plastic cover to the mirror and to ensure that the pouring opening was sealed. In this way, the plastic cover by * heat sealing was hermetically sealed to the surrounding surface of the pouring opening and the surrounding this opening peripheral material and secured to a pulling force was exerted.

Although the closure of the pouring opening of containers with plastic lids in the manner explained is feasible has proven, the pest and resistance norms of the food industry required the tight connection higher between the plastic lid and the lid surface is more resilient than was achievable with the previous techniques.

The present invention is based on the object Avoid disadvantage.

According to the invention, this object is achieved in that the metal surface is first coated with a thermosetting varnish and then provided with an intermediate layer which can be activated by heat and which serves to promote adhesion

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which is earboxy-modified polypropylene resin with a particle size below 5 microns, and that thereafter the polypropylene is hot sealed onto this liner. After that, the heat-sealed surface is immediately applied to the Ambient temperatures cooled.

As will be explained in more detail below, introduces the combined use of a carboxyl modified polypropylene resin with a particle size below 5 microns and the immediate cooling of the metal surface after the propylene polymer has been heat-sealed onto it Surface leads to an unexpected considerable increase in the bond strength of the unit thus created.

An embodiment of the invention is in the drawings shown.

Pig, 1 shows the top view of a tear-open container with a lid for closing the pouring opening, which consists of propylene polymer.

i * ig. Fig. 2 shows a sectional view on an enlarged scale of the container according to FIG. 1 with the sectional plane running along the line 2-2 and shows how the lid made of propylene polymer is attached to the surface of the lid surface according to the invention.

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203292a

To carry out the method designed according to the invention any thermosetting resins or mixtures of thermosetting resins, whose application is common for coating or painting metallic substrates.

Among the typical thermosetting resins used for painting metallic Surfaces that can be used include epoxy resins of A ^ t, which are polyfunctional polymeric reaction products Halohydrins with polyhydric phenols are and the following Have structural formula:

OH ₂ -CH-CH ₂ -

3H, CH,

GH

CH

CH

In the above formula, χ represents the number of condensed Molecules. Typical polyfunctional shark hydrins are Epychlorbydrin, Glycerin, Dißhlorbydrin and the like. Typical polyhydric ones Phenols are resorcinol and a 2,2-bis (4-hydroxyphenyl) alkane. The latter results from the condensation of Phenols with aldehydes and ketones including formaldehyde, acetaldehyde , Propionaldehyde, acetone, methyl ethyl ketone and the like., welone to compounds such as 2,2-bis (4-hydroxyphenyl) propaη and similar connections. Such epoxy resins contain usually epoxy end groups, but epoxy and have hydroxyl end groups.

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Instead of or in a mixture with the epoxy resins can also any resins of the known class of thermosetting phenolic resins can be used, which are obtained by condensation of a phenolic bond be obtained with an aldehyde compound. By Such materials can be used to produce thermosetting lacquer coatings on the metal surface.

Examples of phenols which lead to the formation of phenol-formaldehyde resins are suitable are phenol itself, ortho-, para- and meta-cresols, xylenol, dihydroxybenzenes such as, for example Resorcinol and polynuclear phenols such as naphthol, and the different alkylated, aralkylated, carboxylated, alkylolated, etc. derivatives of these compounds such as O-ethylphenol, canracrol, salicylic acid and the like

Formaldehyde is the one responsible for condensation with phenolic compounds preferred aldehyde compound, “but basically any methylene-containing agent can also be used such as! formaldehyde, paraformaldehyde, Hexamethylenetetramine, acetaldehyde and the like.

Aminaldebydbarze can also be used separately or in combination with epoxy and / or phenolic resins !! ■ be used to create zn to thermosetting Laekübersüge ,,

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The term "Aminaldebydbarz" includes aldebyd condensation products of melamine, urea, acetoguanamine or similar compounds. Generally aldehyde is in the "form of formaldehyde." used, although useful products can also be made from other aldehydes, such as acetaldehyde, crotonaldehyde, Create acrolein, benzaldehyde, furfural and others permit. The amine aldehyde resins commonly used are condensation products of melamine or urea. "

For application to metal surfaces, the abovementioned resins or mixtures of these resins are dissolved in suitable solution systems. Such solution systems are, for example, organic ketones such as methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone and aromatic hydrocarbons such as xylene, toluene and mixtures thereof. By using such solution systems, a coating solution with the necessary viscosity for application can be created . g create a metal surface.

The thermosetting varnishes or compounds are applied to the metal surface as a liquid solution, using the conventional, tried and tested application or coating techniques can be applied in industry. When coating sheet metal for the manufacture of containers roller application is the preferred method because the required application weight easily and conveniently in can be achieved in a single coating process.

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For general coating purposes, however, spray, Dip and flow coatings can be used.

The applied top coat: becomes after an essential Part of the volatile components of the solution systems volatilized is cured to a hard film by applying the coated substrate for a period of 1-10 minutes a temperature between 150-25O ° C is maintained. The preferred coating weight for making Varnish coatings for containers are in the range of 1 - 5 mg

dry coating per 6.45cm surface of the metal base.

The sheet metal stock, the one with the hardened lacquer coating is provided, according to the invention is now equipped with an intermediate layer to promote adhesion or coated containing a carboxyl-modified polypropylene resin.

The carboxy! Modified polypropylene, which is used to carry out of the method designed according to the invention is used is obtained by placing an unsaturated dicarboxylic acid or its anhydride on a polypropylene base is grafted on. Unsaturated dicarboxylic acids or anhydrides, which can be used to make the carboxyl-modified polypropylene resin for carrying out the invention trained process are to produce

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Maleic acid, tetrahydrophthalic acid, fumaric acid, itaconic acid, Uadic acid, methylnadic acid and their anhydrides.

The amount of unsaturated Discarboxylsäure or the amount of anhydride of this acid, which and can be attached grafted onto the polypropylene pad ", is in the range of about 0.05 to about 10 weight percent, calculated on the total weight of the overall by grafting ä wonnenen polymer It has been found, however, that only small amounts of the acid or the anhydride are required in order to give the intermediate layer that property which increases the adhesion or binding capacity with the polymer is expediently in the range from about 0.5-5.0%.

The modified polymers can be prepared by reacting the unsaturated dicarboxylic acid or its anhydride, such as maleic anhydride, are reacted with a propylene to the reaction, has which active breaking points in the molecular structure, which are suitable to attach dicarboxylic acid or its anhydride and au anchor * Active Sites, at which this deposition process occurs, can easily be induced in a known manner in polypropylene, for example by exposing the polypropylene to the action of aoohenergetisohen ionizing radiation or by the polypropylene with fastels or in one

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Solvent is brought into contact, which produces free radicals. These include, for example, dibenzene peroxide, dilauroyl peroxide, dicumyl peroxide, t-butyl perbenzoate and the like. The carboxyl-modified polypropylene resin is preferably prepared in such a way that maleic anhydride is reacted with a solution of polypropylene in an organic solvent which contains a material that produces free radicals . Such a method is described in Belgian patent 607,269. The polypropylene resin used as the raw material for the preparation of the carboxyl-modified polymer can be used as both an amorphous polymer and a crystalline polymer. For a maleic anhydride-modified polypropylene, amorphous polypropylene is generally preferred as the starting material because the carboxyl-modified product is soluble in a variety of common organic solvents at ordinary temperature so that application of the modified polymer is possible using normal solution tea techniques is not soluble in normal solvents, except at relatively high temperatures, and therefore it is generally applied as a dispersion and requires subsequent heating. done in order to bring about the fusion of the applied © © Pariifceloüen.

Ee is a critical and essential wellness program

The present invention that the "fellole size of the mv -

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Carboxyl-modified layer that promotes adhesive force Polypropylene, which is applied to the laek surface of the metal is below 5 microns and is preferably selected in the range between 0.1-4 microns. How more detailed will be explained, there is a significant decrease in the binding force between the propylene polymer and the carboxyl-modified one Polypropylene takes place when the particle size of the carboxyl modified polypropylene is significantly above 5 microns lies.

The intermediate layer that serves to increase the adhesive force carboxyl-modified polypropylenbarζ is generally as a dispersion in a high boiling volatile organic Solvent, such as kerosene, on the painted Metal surface applied, so that a satisfactory alloy of resin particles takes place. The carboxylated polypropylene is expediently applied to the painted metal base applied in a mixture with a polypropylene resin, which has approximately the same particle size, i.e. a size range which has particles of about 0.1-5 microns. Locking in of polypropylene resin in the dispersion improves the flow and viscosity properties of the dispersion in view on the requirements of commercial coating techniques. The polypropylene resin is preferably used in one in the dispersion Weight ratio to the carboxyl-modified polypropylene barζ introduced, which moves from about 85ί 15 to 99: 1.

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The dispersion, which contains carboxyl-modified polypropylene resin, can be applied satisfactorily when the solids content of the dispersion is 15-25 percent by weight of the total weight the dispersion is. In general, a solids content of about 18-23 weight percent is preferred.

The dispersion containing the carboaqyl-modified polypropylene used to increase adhesiveness can be satisfactorily applied by any conventional technique. For the coating of painted metal sheets, which are intended for the production of containers, direct roller application techniques are preferred, because this means that the desired coating can be easily and conveniently applied in a single coating process the coating dispersion can also be used.

After the dispersion has been applied, the solvent is volatilized by heating the coated base. The base is usually heated to a temperature in the range between 175-2OQ ⁰ G and kept at this temperature for about 2-6 minutes to prevent volatilization of the solvent is guaranteed.

In order to have a varnish-overlapping base for propylene polymer covers with an intermediate layer to produceQj that eiae appropriate® To promote the adhesive effect, it is recommended that the coating, which contains the carboxyl-modified polypropylene resin

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contains, to be applied in a strength at which the dry film weight of this intermediate layer is 1.5-3.5 mg dry Coating per 6.45 cm of painted surface can be achieved.

Among the propylene polymers used in accordance with the present invention The modified polypropylene coated metal surface can be bonded to include polypropylene as well as propylene-ethylene copolymers, which contain 1 - 10 $ ethylene *

contain.

The propylene polymer is applied to the intermediate layer of carboxyl-modified polypropylene which, the metal surface covered by heat-sealing at temperatures between 175 225 ⁰ C, preferably at a temperature between 180 - 20O ⁰ O attached. The heat sealing can be carried out using known techniques, for example using heated rails, rods or wires, as well as using an induction | or a high frequency heating.

By heat sealing the propylene polymer with the surface of the carboxyl-modified polypropylene double layer is connected, the unit formed is immediately and severely broken down or cooled down on surrounding external doors, if necessary, by applying cooling technology. De »u include cooling duroh air dream ·, lüblung duroh flitStnd ·« ¥ * «ier, Eint« uoh «n Iq

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Water bath or other suitable measures which do not damage or destruction of the applied or applied Create propylene polymer.

Reference is now made to the figures. In Pig. 1 is the upper end of a container or a container end 10 is shown. J) qs container end 10 is made of metal, for example Made of tinplate, tin-free steel or aluminum. The container end 10 has a central container mirror L 12, on its outer circumference a cover core with one hanging down therefrom extensive Plansch 13 is formed. The Plansch 13 is knurled and double-folded with one after outward-facing splash at the upper end of a container body connected in the usual way.

In the exemplary embodiment shown, the container level 12 is equipped with an outlet opening 14 through which the contents of the container can be poured out of the container. The pouring opening 14 can be produced by stone processing. It is obvious that the opening can have any shape and is not limited to the usual teardrop shape shown as an example.

The outer surface of the container edge © a 10 lit with ® ± nar first layer 15 made of warm-bearable ÜberingslecslE, beiipitlBweia · EpoxT-Uree-Pormaldehyanara γ «rnabeEu ixri Site® urete lag« mum heatable coating is a «await · od« S & iBobenlaf.

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applied to the! Promotion of the adhesive or adhesive force and a carboxyl-modified polypropylene resin, for example a polypropylene-sa-lainic anhydride graft copolymer contains.

A cover is detachable, but tightly closing, on the circumference of the opening 14. 17'aus Propylenpolyraex 'fixed "The cover 17 of the propylene polymer has a lid portion 18, etc. which serves for closing the pouring opening fourteenth Integrally from said cover portion 18 made of a molded pull handle 19 of the. Lid member 18 extends in Ringausfübrung, the lid 17 is connected to the lying around the opening 14 coated surface at a temperature in the range 180-200 ⁰ C.

connected by heat sealing.

The bond created thereby allows the Lid or the lid part can be separated out by applying a tensile force to the * ring or pull handle part 19 ' can. The ring part 19 expediently has an opening which is so big that a finger can be inserted. The heat to achieve the adhesive bond is preferred generated by high frequency heating of the metal surface. 'The high frequency heating is used so that the Heat localized in the peripheral edge area of the pouring opening 14 and bulges in the relatively thin sheet metal, from which the container end 10 consists, can be kept within small limits. In this way, the

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Lid 17 firmly connected to the surrounding area of pouring opening 14 and remains firmly adhered there.

After the lid 17 has been heat-sealed onto the circumference of the pouring opening, the container end 10 is quickly opened Chilled to room temperature.

To explain the nature of the present invention can be practically applied, an example will be explained below. However, it must be taken into account that this example serves only to explain the invention and that the invention is not limited to the specific ones given Materials or process conditions is restricted.

A solution of a mixture comprising 85 percent by weight of an epoxy resin and 15 percent by weight of a ureaformaldehyde resin in a volatile solvent is applied to the surface of a chrome-plated steel sheet Roller applied to produce a paint coating at which the coating weight is 3.5 mg per 6.45 cm. as Epoxy resin available from Shell Chemical Company under the name EPON 1009 was used and as the urea formaldehyde resin, BEETLE 216-18 available from American Cyanamid Company was used. The coating was heated to 213 ° C for 8 minutes in order to volatilize the solvent and the epoxy resin-ureaformaldehyde-

harden the resin mixture to form a hard lacquer film.

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To create the intermediate layer, which serves to increase the adhesion, carboxy-modified polypropylene resin was mixed with finely divided unmodified polypropylene resin in a weight ratio of 5:95. HERCOPRIME PA-672 available from Hercules, Inc. was used as the carboxyl-modified polypropylene resin. This product is a maleic anhydride modified polypropylene with an intrinsic viscosity around 1.7, a carboxyl content j of about 0.6-1 $ and a particle size in the range 0.1-3 microns. The polypropylene resin used by HERCULES INC. available product HERCOTUi ¹ PB-681 is used, which has a melt index of 6 and a particle size in the range of 0.1-2 microns. A 20 # solids dispersion of the carboxyl-modified polypropylene and unmodified polypropylene resin mixture in kerosene was applied to the painted steel surface.

After application, this intermediate layer or dispersion of the carboxyl-modified polypropylene and the unmodified polypropylene ™, the coated sheet at 180 ⁰ C was discolored to remove the solvent to evaporate and cause the 7eracbeelzung Mspergierten particles into a continuous Piim. A strip made of a propylene ethylene copolymer with an ethylene content of 4, Often, a Sobelzindex (D 1238) of 0.55 and a density of 0.895 -o.905 ((D 1505) was placed between two sheet metal strips the one with the intermediate layer of carboxy1-

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modified polypropylene provided metal sheet cut out with the spacers being the propylene-ethylene copolymer strip were facing. The propylene-ethylene copolymer strip had the dimensions 2.45 x 2.45 χ 0.127 cm and consisted of that of the Pirma Shell below under the name SHELL V521. The cut from the metal sheet provided with the intermediate layer Strips measured 2.54 x 2.54 x 0.01524 cm. The unity, which by stacking the two Sheet metal strip with the intermediate plastic strip made of propylene-ethylene copolymer was formed then for heat sealing for 3.5 seconds on a temperature

rature of 204 C and heated with a pressure of 1.4 kg / cm applied.

Immediately after the heat sealing, the layering was done Quenching quenched with water and cooled to room temperature.

The above procedure was repeated using one layer unit was formed, the middle layer of a polypropylene resin lying between the metal sheets a melt index of 4 »0 and a density of 0.905. This is what this polypropylene resin was all about available from Firnn Diamond Shamrock Chemical Company Product DIAMOND 8620.

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The peel strength of the cooled unit layer was then determined. The peel strength of the layer unit is the measure of the load that is required to produce the layer unit pull apart. It was determined by inserting the outer sheet or steel sheet layers of the coating into an angle of 180 ° to the adhesive bond in an Instron machine pulled apart at a rate of 1.27 cm per minute.

For the purpose of comparison, the above has been explained The procedure was repeated in several separate experiments, although variations were made in each case by for example, the heat-sealed layer unit is not quenched or a carboxyl modified polypropylene having a particle size above 5 microns was used. The peel strengths determined for the layer units were compiled in the following table:

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Try composition
No. of the liner

Particle size of the carboxyl treatment of the peel strength modified polypropylene unit
resin (micron)

1 Propylene-Ethylene-0 op polymer 2 deterred * 5.37 2
CD Propylene-Ethylene-Co polymer 2 not departed
frightens 4.80 Propylene-ethylene copolymer 10 deterred 4.09 Polypropylene 2 deterred 2.79 5 Polypropylene 2 not departed
frightens 2.07 6th Polypropylene 10 deterred 1.55

* "deterred" means that the superimposed unit immediately "after the Heat sealing was cooled to room temperature.

CQ K) OO

By referring to the table above, first evident- that the peel strength of the propylene polymer, which is connected to the metal surface, which according to the present invention with an intermediate layer for conveying the adhesive strength was equipped, which carboxyImodi- ' fied polypropylene resin contains (tests 3Jr. 1 and 4) is hereditary greater than the peel strength, which in opposing tests or control tests (test no. 2, 3 »5 and 6) in which the heat-sealed layer unit was not immediately cooled or in which a carboxyl modified polypropylene having a particle size greater than 6 microns was used.

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Claims (13)

1 · .JProcess for pretreating metal objects the surface of an object. is to be glued to a propylene polymer, characterized in that that a) a top coat is applied to the metal surface, b) an intermediate layer is applied to the top coat to promote the bond strength is, the carboxyl modified polypropylene resin with a particle size of less than 5 microns, c) a layer of propylene polymer is heat-sealed onto the intermediate layer, and d) the sealed egg unit immediately after Heat sealing is cooled to ambient temperature. 2. The method according to claim 1, characterized in that that uses a carboxyl-modified polypropylene resin having about 0.05 to 5 $ carboxyl groups will. 3. The method according to claim 1, characterized in that that as a carboxyl-modified polypropylene resin the reaction product "tob polypropylene and an unsaturated Dioarb.oxylsäur® or the anhydride this acid is used » 10-9811 / 176? . - 23 - 4. Method according to Amsprucb 1, thereby ge ken η— ζ ei c h η et that as unsaturated anhydride J maleic anhydride is used. 5. The method according to claim 1, characterized in that g e k e η η, that a carboxyl modified polypropylene resin with a particle size between about 0.1 ms 3 microns is used. 6. The method according to claim 1, characterized in that for the Zwischenlage.ein mixture made of a carboxy! modified polypropylene resin and a polypropylene resin is used, which is "both one Have particle size below 5 microns. 7. The method according to claim 1, since you roh g e ke η η ze I h η e t that the propylene polymer is polypropylene is used. 8. The method according to claim 1, since d u r c h g e k e η η draws, that the propylene polymer is a propylene-ethylene copolymer is used.. 9. Pull-open part with a container mirror, which is with a üacküoerzug is provided and a preformed one has opening which is closed with an extremely separable lid, thereby g e k eη η - 109811/1767 shows that the cover (17) is made of a propylene polymer and on the surface of the mirror (12) surrounding the hole (14) by means of an intermediate layer (16) is heat sealed to promote the adhesive bond is used between the lid and the mirror and a carboxyl-modified polypropylene resin with an underneath 5 Mkron lying particle size, and that the entire Unit (10) is cooled to ambient temperature immediately after heat sealing. 10. The tear-open container part according to claim 9, characterized in that the carboxyl-modified one Polypropylene resin contains about 0.1 to 5 $ carboxyl groups. 11. The tear-open container part according to claim 9, characterized in that characterized in that the carboxyl modified polypropylene resin is the reaction product of polypropylene and an unsaturated dicarboxylic acid or anhydride is. 12. Tear-open container part according to claim 9, characterized in that the unsaturated anhydride Maleic anhydride is provided. 13. Tear container part according to claim 9® thereby characterized in that the oartooaqrl modified Polypropylene resin has a particle size in the range between 0.1 to 2 microns. 10 9 811/17 6? , - 25 - ■■■ ... ■ H. Aufreiß »e holds according to claim 9, d a d u r c h g e k e η η draws η e t that as a propylene polymer Polypropylene is provided. 11/1767 Emptied